Gantz spoke to journalists after Netanyahu called for them to join together in a unity government as results from Tuesday’s vote showed neither with an obvious path to form a majority coalition.
Gantz’s centrist Blue and White is nevertheless two seats ahead of Netanyahu’s right-wing Likud, according to results published by Israeli media with 97 percent of the vote counted.
The ex-military chief said his alliance had the most seats and he should lead the next government.
“The public voted clearly in favour of unity,” Gantz said.
“Blue and White has at the time I am speaking won 33 seats, while Netanyahu has not obtained a sufficient majority to form a coalition as he hoped.”
He went on to say that “we will listen to everyone, but we will not accept mandates imposed on us.”
Netanyahu has been seeking to find a way to remain in office and continue his reign as Israel’s longest-serving prime minister.
He also faces the possibility of corruption charges in the weeks ahead.